Operation and performance of a second generation, solid state, star tracker, the ASC

The Advanced Stellar Compass (ASC) is a second generation star tracker, consisting of a CCD camera and its associated microcomputer. The ASC operates by matching the star images acquired by the camera with its internal star catalogs. An initial attitude acquisition (solving the lost in space problem) is performed, and successively, the attitude of the camera is calculated in celestial coordinates by averaging the position of a large number of star observations for each image. Key parameters of the ASC for the Ørsted satellite and Astrid II satellite versions are: mass as low as 900 g, power consumption as low as 5.5W, relative attitude angle errors less than 1.4 arcseconds in declination, and 13 arcseconds in roll, RMS, as measured at the Mauna Kea, HI observatories of the University of Hawaii in June 1996.